1. Field of the Invention
The present invention relates to writing implements and, more particularly, to a pen that automatically guides in outside air pressure subject to the level of ink in the reservoir tube to smoothen the writing.
2. Description of the Related Art
A regular pen A1, as shown in FIG. 1, comprises a penholder A2 and an ink cartridge and writing tip assembly A3 provided in the penholder A2. This design of pen is not satisfactory in function because of the following drawbacks.
1. When the ink in the ink cartridge and writing tip assembly A3 used up, the whole ink cartridge and writing tip assembly A3 becomes useless and must be thrown away.
2. When the writing tip of the ink cartridge and writing tip assembly A3 is damaged by an accident, the writing tip cannot be replaced with a new one, and the ink cartridge and writing tip assembly A3 becomes useless and must be thrown away.
The present invention has been accomplished under the circumstances in view. It is the main object of the present invention to provide a pen, which enables the user to refill the desired color of ink. It is another object of the present invention to provide a pen, which uses a replaceable writing tip. It is still another object of the present invention to provide a pen, which is provided with a spare writing tip for replacing the main writing tip when the main writing tip damaged accidentally. It is still another object of the present invention toprovide a pen, which is suitable for industrial use. To achieve these and other objects of the present invention, the pen comprises a reservoir tube holding a reservoir tube and a writing tip at one end for writing, a barrel fastened to one end of the reservoir tube remote from the writing tip by a connector to hold a barrel, a top cap capped on the barrel and adapted to hold a spare writing tip, a spring holder fixedly provided inside the barrel to hold a spring holder, and a movable stopper supported on a spring at the spring holder and adapted to open an air passage hole between the atmosphere and the inside space of the reservoir tube subject to the level of ink in the reservoir tube.